JP3527844B2 - Multi-branch optical line test method and apparatus - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-branch optical line for branching a plurality of lines (optical lines) to measure a fault occurrence time, a fault occurrence line and a fault occurrence distance of the multi-branch optical line. The present invention relates to a road test method and apparatus.

[0002]

2. Description of the Related Art FIG. 10 is a block diagram showing a configuration example of a conventional multi-branching optical line test apparatus. This multi-branch optical line test device is for performing a fault isolation test of the 8-branch optical line provided in the 1.31 / 1.55 wavelength division multiplexing transmission system. In this figure, OTD
The test light (1.6 μm band) emitted from the R measuring device 1 is
The light enters the optical line 3 via the coupler 2, is branched by the star coupler 4, and is then distributed to the optical fibers fb1 to fb8.

ONU (Op of each optical fiber fb1 to fb8
Filters 41 to 48 are respectively provided in front of a (tical network unit). The filters 41 to 48 have a pass band characteristic of passing only the signal light for each ONU and reflecting the test light. Therefore, the test lights that have traveled through the optical fibers fb1 to fb8 are reflected by these filters 41 to 48, and the reflected lights of the filters 41 to 48 are optical fibers fb1.
~ Fb8 will be reversed. Then, these reflected lights are combined by passing through the star coupler 4, and returned to the OTDR measuring device 1 as response light via the coupler 2. The response light returned in this way is OTDR
It is analyzed by the measuring instrument 1.

FIG. 11 is a graph showing an example of a waveform of response light observed by the OTDR measuring device 1. The waveform shown in this figure shows a time-series change of the response light, but in FIG. 11, a value obtained by multiplying the propagation time of the response light by the transmission speed of the light (that is, the response light has propagated). The length of the optical fiber is the horizontal axis. Here, the response light is obtained by combining the reflected lights of the filters 41 to 48, and these filters 41 to 48 are provided at positions different in distance from the OTDR measuring device 1. Therefore, O
Each filter 41 to 4 observed by the TDR measuring device 1
The reflected lights from 8 do not overlap on the time axis and are observed separately. In FIG. 11, the waveform R shown on the leftmost side is the reflected light from the star coupler 4, and the optical fiber fb is sequentially arranged from the waveform R toward the right side.
The waveform of the reflected light returned to the OTDR measuring instrument 1 via 1 to fb8 is displayed.

FIG. 12 is an enlarged graph showing the waveform of the reflected light returned from the response light observed by the OTDR measuring device 1 via the optical fibers fb6 to fb8. Here, FIG. 12A shows a case where no failure occurs in any optical fiber, and FIG. 12B shows a failure simulated by giving a bending loss of 3 dB to the optical fiber fb7. The case is shown. As shown in these figures, it can be seen that, with respect to the optical fiber fb7, the intensity of the reflected light is reduced due to the simulated occurrence of the failure.

As described above, according to the configuration shown in FIG.
By analyzing the intensity of each reflected light in the response light returning to the OTDR measuring device 1, it is possible to detect the fault occurring in the optical line. Regarding this technology, 1994
Paper B-846 at the IEICE Autumn Meeting
"1.6μm band fault isolation test technology for branch type optical line"
Is disclosed in.

[0007]

By the way, in the above-mentioned conventional multi-branched optical line test apparatus, the optical line in which a fault has occurred can be specified, but the distance (position) of the fault occurrence point in the optical line. There was a problem that could not be detected. Further, in the above-mentioned conventional multi-branched optical line test apparatus, for each branched optical fiber, the filter to be installed in the optical fiber, it is necessary to install so that the distance from the coupler to the filter is different from each other, There is a problem that the fiber length is limited. Further, in the above-mentioned conventional multi-branched optical line test device, there is a problem that the system becomes expensive because a filter must be provided for each optical fiber.

The present invention has been made under such a background, and a multi-branch optical line test method capable of automatically detecting a fault occurrence time, a fault occurrence line and a fault occurrence distance of the multi-branch optical line. And to provide a device.

[0009]

The invention according to claim 1 is
A first process of introducing an optical pulse into a branch point of a multi-branched optical line branched into a plurality of optical lines, and a second process of receiving response light in which reflected light of the optical pulse in each part of each optical line overlaps Process, a third process of logarithmically converting the waveform data obtained by converting the response light into an electric signal, a fourth process of calculating an approximate straight line for the logarithmically converted waveform data, and a logarithmically converted waveform. A fifth step of comparing the data with the approximate straight line to detect a Fresnel reflection point in the waveform data; and a sixth step of dividing the waveform data using the Fresnel reflection point as a division point. And a seventh step of calculating an attenuation constant of each optical line by performing an attenuation constant separation analysis for each range, and an eighth step of storing the calculated attenuation constant in a storage device in association with a measurement time, First
After the eighth step is repeated at regular intervals, the failure occurrence time in the multi-branched optical line is determined based on the change in the attenuation constant stored in the storage device.
And a ninth step of determining a fault occurrence line and a fault occurrence distance. According to a second aspect of the present invention, in the multi-branched optical line test method according to the first aspect, the logarithmic conversion formula in the third step is yn = 5log.
(Xn) where xn is the waveform data and yn is logarithmically converted waveform data. Claim 3
A fifth aspect of the present invention is the method for testing a multi-branched optical line according to any one of the first and second aspects, wherein the fifth step is based on an intersection between the logarithmically converted waveform data and the approximate straight line. The Fresnel reflection point is detected. The invention according to claim 4 is the method for testing a multi-branched optical line according to any one of claims 1 to 3,
In the ninth step, the attenuation constants are compared between measurement times, and when the attenuation constants change, it is determined that a failure has occurred,
Judge that the measurement time when the damping constant has changed is the time of failure occurrence,
Judge the distance of the reflection peak at the position where the attenuation constant has changed ,
It is characterized in that the optical line in which the distance of the reflection peak has changed is determined to be the failure occurrence line, and the distance of the reflection peak after change is determined to be the failure occurrence distance. According to a fifth aspect of the present invention, light emitting means for introducing an optical pulse into a branch point of a multi-branched optical line branched into a plurality of optical lines, and response light in which reflected light of the optical pulse in each part of each optical line overlap. Light receiving means, a converting means for logarithmically converting the response light into an electric signal, and an approximation means for calculating an approximate straight line for the logarithmically converted waveform data, and a logarithmically converted waveform. Comparing the data and the approximate straight line, comparing means for detecting a Fresnel reflection point in the waveform data, dividing means for dividing the waveform data using the Fresnel reflection point as a division point, and for each divided range Analyzing means for performing attenuation constant separation analysis to calculate the attenuation constant of each optical line, writing means for storing the calculated attenuation constant in a storage device in correspondence with the measurement time, and processing by the above-mentioned means. And a failure occurrence time, a failure occurrence line, and a failure occurrence distance in the multi-branched optical line based on an attenuation constant stored in the storage device. It is characterized by doing. Claim 6
According to a fifth aspect of the present invention, in the multi-branched optical line test apparatus according to the fifth aspect, the logarithmic conversion formula in the conversion means is yn = 5.
log (xn) where xn is the waveform data and yn is logarithmically converted waveform data. According to a seventh aspect of the present invention, in the multi-branched optical line test apparatus according to the fifth aspect or the sixth aspect, the comparison means is based on an intersection between the logarithmically converted waveform data and the approximate straight line. , The Fresnel reflection point is detected. The invention according to claim 8 is the multi-branched optical line test apparatus according to any one of claims 5 to 7, wherein the determination means compares the attenuation constants between measurement times, and the attenuation constants change. Then, it is determined that a failure has occurred, the measurement time at which the attenuation constant has changed is determined to be the failure occurrence time, the position at which the attenuation constant has changed is determined as the distance of the reflection peak, and the optical path where the distance of the reflection peak has changed is determined. Is determined to be the fault occurrence line, and the distance of the reflection peak after the change is determined to be the fault occurrence distance.

[0010]

DETAILED DESCRIPTION OF THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a configuration example of a multi-branching optical line test apparatus according to an embodiment of the present invention. In this figure, MS1 is an OTDR measuring device, and SW1 is a memory in which software for data analysis is stored. FB1 to FB4 are branch optical fibers, and ED1 to ED4 are terminators of the branch optical fibers. Further, CP1 is an optical coupler, CN1 to CN4 are connectors for connecting the optical coupler CP1 and the branched optical fibers FB1 to FB4, and CN5 is the optical coupler CP1 and the OTDR measuring device M.
It is a connector for connecting to S1. Optical coupler CP
1, branch optical fibers FB1 to FB4 and terminator ED1
~ ED4 constitutes a test target in the present embodiment. Then, with respect to this test object, the OTDR measuring device MS1 connected through the coupler CP1 and the OTD
The memory SW1 storing the software executed by the R measuring device MS1 constitutes the multi-branched optical line test apparatus according to the present embodiment. Although not shown in FIG. 1, the present apparatus has a large-capacity measurement result storage device (hard disk or the like) that stores the measurement result of the OTDR measuring device MS1.

Next, the operation of the multi-branched optical line testing device having the above-mentioned configuration will be described. (1) Acquisition of OTDR waveform data When the OTDR measuring device MS1 emits an optical pulse, the optical pulse is split by the optical coupler CP1 and each branched optical fiber F
It is incident on B1 to FB4. Each branch optical fiber F
The backscattered light generated in B1 to FB4 is overlapped by the optical coupler CP1 and returns to the OTDR measuring device MS1 as response light. The response light is converted into an electric signal according to the level inside the OTDR measuring device MS1. The converted electric signal is stored in the memory as OTDR waveform data (digital waveform data).

FIG. 2 is a graph showing an example of OTDR waveform data when no fault has occurred in any of the branch optical fibers. In this figure, the horizontal axis indicates distance, and points on the horizontal axis indicating each data (point)
The point corresponds to 2 m. That is, for example, 2
0000 points correspond to 40 km (= 2 m × 20000). In addition, in this figure, the vertical axis represents the level of the backscattered light of each of the branch optical fibers FB1 to FB4. This OTDR waveform data is used for each branch optical fiber FB.
The backscattered lights of 1 to FB4 are variously overlapped. Further, in FIG. 2, ED1 to ED4 are waveforms of reflection peaks at the terminators of the branched optical fibers FB1 to FB4, respectively. On the other hand, CP is a waveform of the reflection peak of the connector connected to each of the branched optical fibers FB1 to FB4 in the coupler CP1.

(2) Waveform Analysis FIG. 3 is a flow chart showing an example of an OTDR waveform data analysis process by the test apparatus. First, in step S1, OTDR waveform data (linear waveform data: waveform of FIG. 2) is converted into logarithmic waveform data. The conversion formula to logarithmic waveform data in the present embodiment is the following formula (1). yn = 5log (xn) (1) where xn is the level of the backscattered light (optical power) received by the OTDR measuring instrument MS1. ) Is shown. Also, x
The subscript n of n is the number of each point on the horizontal axis of the graph shown in FIG. 2 (n = 1, 2, 3, ..., 20000)
Indicates. That is, in xn, x1 represents the level of backscattered light from the 2m (= 2m × 1) point in the graph shown in FIG. 2, and x20000 represents 40km (= 2m × 200).
00) represents the level of backscattered light. 20,000 linear waveform data xn according to equation (1)
Is converted into 20000 logarithmic data yn. Figure 4
3 is a graph obtained by converting the graph (linear waveform data) shown in FIG. 2 into logarithmic waveform data.

In step S2, an approximate straight line y = is applied to the logarithmic waveform data shown in FIG. 4 by using the least squares approximation method.
a1 · d + b1 (straight line D1 in FIG. 4) constants a1 and b
Calculate 1. Next, as shown in FIG.
The points where 1 intersects the waveform after logarithmic conversion are Pu0, Pd0, P
u1, Pd1, ..., Pu4, Pd4, and the distances d (Pu0), d (Pd0), ..., d (Pd
4) is calculated. Then, the distances d (Pu0), d (Pd
0) based on the rising point PU0 of the reflection peak CP
And the distance of the falling point PD0 is calculated. In the same manner, the rising points PU1 of the reflection peaks ED1 to ED4
~ PU4 and the distances of the falling points PD1 to PD4 are calculated.

In step S3, the OTDR waveform data shown in FIG. 2 is divided using the reflection peak (Fresnel reflection point) as a division point. In this embodiment, the OTD shown in FIG.
The R waveform data is divided into the following ranges (L1 to L4). L1: between point PD0 and point PU1 L2: between point PD1 and point PU2 L3: between point PD2 and point PU3 L4: between point PD3 and point PU4 After the waveform division, attenuation constant separation analysis is performed for each range L1 to L4, Calculate the damping constant. FIG. 5 is a table showing an example of an attenuation constant and its determination when no failure occurs in any of the branch optical fibers.

In step S4, the attenuation constant calculated in step S3 is stored in the measurement result storage device (not shown). The processing of steps S1 to S4 described above is
It is repeated at regular intervals. In the present embodiment, since the measurement is performed once at a fixed time, the measurement times are t1, t2,
..., tk, tk + 1, tk + 2, .... This measurement time is recorded in the measurement result storage device together with the attenuation constant measured at the measurement time in step S4.

Here, for example, as shown in FIG. 6, consider a case where a failure occurs at point x of the branch optical fiber FB3 at time tk + 1. In this case, the OTDR measuring device MS
The OTDR waveform data captured in 1 changes from the waveform shown in FIG. 2 to the waveform shown in FIG. In FIG. 7, ED
3'is a waveform of a reflection peak at the point x of the branched optical fiber FB3.

After capturing the OTDR waveform data shown in FIG. 7, the process proceeds to step S1 (see FIG. 3), and
The R waveform data (linear waveform data) is converted into logarithmic waveform data shown in FIG. Next, in step S2, an approximate straight line y = a2.d + b2 (straight line D2 in FIG. 8) is applied to the logarithmic waveform data shown in FIG. 8 by using the least squares approximation method.
The constants a2 and b2 of Then, the distances between the rising points PU0 ′ to PU4 ′ and the falling points PD0 ′ to PD4 ′ of the reflection peaks CP to ED4 are calculated by the same method as in the case where no failure has occurred (see FIG. 4).

In step S3, the OTDR waveform data shown in FIG. 7 is divided into L1 'to L4' using the reflection peak (Fresnel reflection point) as a division point, and each range L is divided.
A damping constant separation analysis is performed for 1 ′ to L4 ′. Figure 9
[Fig. 6] is a table showing an example of an attenuation constant and its determination when a failure occurs in the branch optical fiber FB3. In step S4, the attenuation constant calculated in step S3 is stored in the measurement result storage device (not shown) as the measurement result at the measurement time tk + 1. As described above, by repeating the processes of steps S1 to S4, the measurement result storage device stores the attenuation constants at the measurement times t1 to tk (see FIG. 5) and the attenuation constants at the measurement time tk + 1 (see FIG. 9). Will be stored.

After the processing of steps S1 to S4 is completed,
In step S5, the failure occurrence time, the failure occurrence line, and the failure occurrence distance are determined based on the attenuation constant stored in the measurement result storage device (not shown). This determination processing will be described by taking the above-described failure (when a failure occurs at the point x of the branch optical fiber FB3 at time tk + 1: see FIG. 6) as an example. In this case, since there is no change in the damping constant from time t1 to time tk (see FIG. 5), it is determined that no failure has occurred. On the other hand, time tk → time tk + 1
Then, since the attenuation constant changes (FIG. 5 → FIG. 9), it is determined that a failure has occurred. At this time, since the change of the damping constant occurs between the time tk and the time tk + 1, it is determined that a failure has occurred during this time. As for the faulty line, the branch optical fiber FB3 in which the position of the reflection peak has changed
Is the faulty line. Further, regarding the fault occurrence distance (position), the fault occurrence distance is the reflection peak ED.
Judge as 3'distance. As described above, the test apparatus can automatically detect the failure occurrence time, the failure occurrence line, and the failure occurrence distance of the multi-branched optical line.

The embodiment of the present invention has been described in detail above with reference to the drawings. However, the specific configuration is not limited to this embodiment, and the design change and the like without departing from the gist of the present invention. Even this is included in this invention. For example, in the above-described embodiment, steps S1 to S
After repeatedly performing the process of 4 to obtain the attenuation constant at each time, various determinations of the failure are made in step S5, but it is also possible to repeat the processes of steps S1 to S5. That is, it is conceivable that each time a damping constant is obtained at regular time intervals, various determinations of a failure may be made (by comparing with the damping constant at the immediately preceding time) in step S5. In this case, it is possible to make various kinds of judgments on the fault almost in real time. Further, in the same embodiment, 4
Although an example of a branch type optical line is shown, the number of branches of the target multi-branch optical line is not limited to this, and the present invention is
It is possible to support a multi-branched optical line with an arbitrary number of branches.

[0022]

As described above, according to the present invention, the failure occurrence time, the failure occurrence line, and the failure occurrence distance of the multi-branched optical line can be automatically detected. Therefore, it is possible to efficiently perform these measurement operations without installing filters at different intervals for each line when measuring a faulty line as in the conventional case. In addition, in this multi-branched optical line test device, the same measurement operation is always performed by the device, so that it is possible to perform measurement with higher objectivity and reliability as compared with the case where a person performs measurement. Is.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration example of a multi-branched optical line test device according to an embodiment of the present invention.

FIG. 2 is a graph showing an example of OTDR waveform data (linear waveform data) in the case where no failure has occurred in any of the branch optical fibers.

FIG. 3 is a flowchart showing an example of an OTDR waveform data analysis process according to the present embodiment.

FIG. 4 is a graph showing an example of OTDR waveform data (logarithmic waveform data) when no failure occurs in any of the branch optical fibers.

FIG. 5 is a table showing an example of an attenuation constant and its determination when no failure occurs in any of the branch optical fibers.

FIG. 6 is a block diagram showing an example of a failure occurrence point.

FIG. 7 is a graph showing an example of OTDR waveform data (linear waveform data) when a failure occurs in the branch optical fiber FB3.

FIG. 8 is a graph showing an example of OTDR waveform data (logarithmic waveform data) when a failure occurs in the branch optical fiber FB3.

FIG. 9 is a table showing an example of an attenuation constant and its determination when a failure occurs in the branch optical fiber FB3.

FIG. 10 is a block diagram showing a configuration example of a conventional multi-branched optical line test apparatus.

FIG. 11 is a graph showing a waveform example of response light observed by a conventional multi-branched optical line test apparatus.

FIG. 12 is an optical fiber fb of the response light shown in FIG.
It is the graph which expanded and showed the waveform of the reflected light corresponding to 6-fb8.

[Explanation of symbols]

MS1 ... OTDR measuring instrument, SW1 ... memory, FB
1-FB4 ... Branched optical fibers, ED1-ED4 ...
Terminator, CP1 ... Coupler, CN1-CN5 ... Connector

─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Keiichi Shimizu 3-3-2 Nakanoshima, Kita-ku, Osaka City, Osaka Prefecture Kansai Electric Power Co., Inc. (72) Inventor Koichi Shinozaki 3--3 Nakanoshima, Kita-ku, Osaka City, Osaka Prefecture No. 22 In Kansai Electric Power Co., Inc. (72) Inventor Takashi Motoji 3-3-22 Nakanoshima, Kita-ku, Osaka-shi, Osaka Kansai Electric Power Co., Inc. (56) Reference JP-A-9-329526 (JP, A) 59-61739 (JP, A) JP 5-126674 (JP, A) JP 9-269248 (JP, A) JP 11-6785 (JP, A) (58) Fields investigated (Int .Cl. ⁷ , DB name) G01M 11/00-11/08

Claims (8)

(57) [Claims] 1. A first process of introducing an optical pulse into a branch point of a multi-branched optical line branched into a plurality of optical lines, and a response light in which reflected light of the optical pulse in each part of each optical line overlaps with each other. A second step of receiving light, a third step of logarithmically converting the waveform data obtained by converting the response light into an electric signal, and a fourth step of calculating an approximate straight line for the logarithmically converted waveform data, A fifth step of comparing logarithmically converted waveform data with the approximate straight line to detect a Fresnel reflection point in the waveform data, and a sixth step of dividing the waveform data using the Fresnel reflection point as a division point. Step 7: Attenuation constant separation analysis is performed for each divided range, and a seventh step of calculating the attenuation constant of each optical line, and 8th step of storing the calculated attenuation constant in a storage device corresponding to the measurement time The process of After the process from the process of the eighth it was repeated every predetermined time, based on the change of the attenuation constant stored in the storage device, the multi-branch optical network failure at time, fault occurrence line and fault 9. A multi-branched optical line test method, comprising: a ninth step of determining a generation distance. 2. The method for testing a multi-branched optical line according to claim 1, wherein the logarithmic conversion formula in the third step is yn =
5log (xn) where xn is the waveform data, yn
Is a logarithmically converted waveform data, the multi-branched optical line test method. 3. The multi-branched optical line test method according to claim 1, wherein the fifth step is based on an intersection between the logarithmically converted waveform data and the approximate straight line. A method for testing a multi-branched optical line characterized by detecting the Fresnel reflection point. 4. The multi-branched optical line test method according to claim 1, wherein in the ninth step, the attenuation constant is compared between measurement times, and the attenuation constant changes. , It is judged that a failure has occurred, the measurement time when the attenuation constant has changed is judged as the failure occurrence time, and the position where the attenuation constant has changed is judged the reflection peak distance.
A method for testing a multi-branched optical line, characterized in that an optical line in which the distance of the reflection peak has changed is determined to be a faulty line, and the changed distance of the reflection peak is determined to be the faulty distance. 5. A light emitting means for introducing an optical pulse into a branch point of a multi-branched optical line branched into a plurality of optical lines, and a response light in which reflected light of the optical pulse in each part of each of the optical lines overlaps. Light receiving means, conversion means for logarithmically converting the waveform data obtained by converting the response light into an electric signal, approximation means for calculating an approximate straight line for the logarithmically converted waveform data, and logarithmically converted waveform data and the Comparison means for comparing Fresnel reflection points in the waveform data by comparing with an approximate straight line, dividing means for dividing the waveform data with the Fresnel reflection points as division points, and attenuation constant separation for each divided range. An analysis unit that analyzes and calculates the attenuation constant of each optical line, a writing unit that stores the calculated attenuation constant in a storage device corresponding to the measurement time, and a process by each unit After being repeatedly performed for each constant time, based on the change of the attenuation constant stored in the storage device, time of failure in the multi-branch optical network, a determining means for determining a fault occurrence line and fault distance A multi-branched optical line test apparatus comprising: 6. The multi-branched optical line test apparatus according to claim 5, wherein the logarithmic conversion formula in the conversion means is yn = 5log.
(Xn) where xn is the waveform data and yn is logarithmically converted waveform data. 7. The multi-branched optical line test apparatus according to claim 5, wherein the comparison means is based on an intersection point between the logarithmically converted waveform data and the approximate straight line. A multi-branched optical line test device characterized by detecting a reflection point. 8. The multi-branched optical line test apparatus according to claim 5, wherein the determination unit compares the attenuation constants between measurement times, and when the attenuation constant changes, a failure occurs. Is determined to have occurred, the measurement time at which the attenuation constant has changed is determined to be the failure occurrence time, and the position at which the attenuation constant has changed is determined as the reflection peak distance.
A multi-branch optical line test apparatus, characterized in that an optical line in which the distance of the reflection peak has changed is determined to be a failure occurrence line, and the changed reflection peak distance is determined to be the failure occurrence distance.